One of the most familiar method of controlling the flow through a pipe line is to install a control valve that provides a variable area of the valve opening by partially opening or partially closing the valve. In such flow control valves wherein the area of the valve opening is varied, the flow of a fluid medium through the valve opening is a complex nonlinear function of the area of the valve opening and, consequently, the flow control valve itself does not provide information on the rate of fluid flow through the flow control valve.
The primary object of the present invention is to provide a flow control valve that has the dual functions of flow control and flow measurement.
Another object is to provide a stepper control valve including a plurality of orifices or nozzles wherein the valve controller closes and opens different numbers of the orifices in a stepwise control of the flow, providing fluid flow proportional to the number of the orifices open in a combination selected by the valve controller.
A further object is to provide a stepper control valve including a plurality of rotary closure members respectively blocking a plurality of flow passages extending from one port opening to the other port opening included in the valve body, wherein each rotary closure member includes a one or more orifices or nozzles which open each flow passage blocked by each rotary closure member when the rotary closure member is rotated to the open position.
Yet another object is to provide a stepper control valve of the aforementioned objects having a plurality of orifices or nozzles of equal throat section area.
Yet a further object is to provide a stepper control valve of the aforementioned objects having a plurality of the orifices or nozzles having different throat section area.
Still another object is to provide a stepper control valve exclusively employing rotary seals only without using any sliding seals.
Still a further object is to provide a stepper control valve of light weight and compact bulk.
These and other objects of the present invention will become clear as the description thereof proceeds.